This invention is directed to an analog-to-digital tester, and in particular to an analog-to-digital tester including an analog-to-digital converter having two ranges of full scale sensitivity differing by a multiple of ten to two attenuation levels differing by a multiple of a hundred whereby in combinations of sensitivity and attenuation four ranges are provided for display.
Heretofore, in the prior art, digital display testers for producing digital representations of voltage, current, resistance and the like, have been provided with manual or automatic range changing circuitry. For example, when a voltage is applied to the input circuitry, the range of the voltage is detected by automatic range changing circuitry, which circuitry selects an attenuation level corresponding to the range of the voltage to be measured. Attenuation is effected by selectively energizing relays associated with the specific range of attenuations. However, power consumption in such relays is excessive and the cost of such relays in miniaturized circuitry is considerable. The attenuation network in conventional digital output testers includes a network of resistors usually having ratios of resistance, one to the other, of 1:1, 1:10, 1:100 and 1:1000. These ratios must be very accurately produced and the resistor elements must have high resistance to voltage breakdowns. As such the attenuator is one of the most expensive parts in the conventional digital tester. Although efforts have been made to substitute semiconductor switches for the relays, such efforts have been less than completely satisfactory due to the resistance breakdown voltages which are required. Accordingly small size in the attenuators and in the switches has not been achieved
What is needed is an analog-to-digital tester in which the number of components in the attenuator circuitry is reduced, the number of switch contacts is reduced, the voltage breakdown requirements are reduced and wherein semiconductor switches are utilized to replace bulkier components and miniaturization is thereby achieved.